Vulcanizing rubber



Patented Oct. 27, 1925.

UNITED STATES PATENT OFFICE.

GEORGE H. STEVENS. 0F NEWARK, NEW JERSEY. I

' VULC ANIZING RUBBER.

No Drawing. Original application filed June 25, 1923, Serial No.647,765. Divided and this application filed January 26, 1925. Serial No.4,958.

To all whom t may concern:

Be it known that I, Guonin-x ll. S'rnvnNs,

a citizen of the United States. residing at Newark, in the county ofEssex and State of New Jersey, have invented a certain new and usefulimprovement in Vuleanizing Rubber, of which the following is aspecification.

This invention relates to improvements in the use of organic nitrogenoussubstances that assist in or accelerate the'vuleanization of rubber, andhas for its object the utilization of new products that are mentionedfor this purpose.

The use of organic nitrogenous compounds in the vulcanization of rubberis quite general and the products so used are technical- -lytermedaccelerators? Whether such bodies act as catalysts, sulphur carriers,polymerizers, activators, or accelerators, is not the purpose of thisspecification to discuss, but I make use of the conventional termaccelerator in my mention of them.

In experimental work with various nitrogenous organic bodies that Iliaveused, to assist in the vulcanization of rubber, I have found-thatcertain derivatives of carbodiimides form exceedingly valuable productsfor this purpose, and contrary to the 39 general impression that theyare not suitable for use in rubber vulcanization} In a previous patentapplication No.

399,979 I have mentioned tetraphenylinelamine(tetraphenyltricarbodiimide) 27 22 c CHI-I2 o 5) 4N0 a phenylatedcarbo-diimide as an accelerator, and I have-also found that otherderivatives of carbodiimides are also very etticient aids tovulcanization, and especially where tlmy are markedly basic incharacter.

An example of such a product is tetralolylmelamine,(tetratoly'ltriearbodiiu'lide) expressed by tliei'ollowing formula:

This product has a nitrogen content of over 17% and is comparativelystable during the period, and at the usuaLtemperatuies of vulcanization.

This product can be produced in various ways, but one'nninner is tounite 2 molecules of carbotolyliinidc, (C H N with 1 molecule ofcarboditolvlimide,

vbut with a somewhat producing 1 molecule of tetrntolyltricarbodiimide.J The same molecular wreentages of the polymeric forms respectively, o'tthese same carbo-tolylimides, also produce tctratolytri- 'arbodiimide.

This identities the product then as a dcrivative of earbodiimid'e.

C NII} I NI-I A similar product, results from the correspondingv unionof 9 molecules of carboxylilimide, (C H N with one molecule ofcarbodixylilimide, (C H NcczNc H which then would betetraxyliltricarbodiimide, C,, -,I-I N,,:C' H (C H N This body alsoproves a'good accelerator lower nitrogen content.

One method of obtaining carbo- (mono ordi substituted) -imidcs, is bydesulphurizing the corresponding substituted thioureas. Suchdesulphurizing is however subject to many modifications, depending onthe presence of other products, and so mixed products may result.

For instance-mustard oil is frequently present in di'substitutedtliiourea. If desulphurization of di substituted thiou rea takes placethen in the presence of ammonia and mustard oil, a formation of thecorresponding monO- substituted thiourea could take place, and adesulphurization of both -thioureas would then yield the twocorresponding carbo-substitutcd -imides.

These carbo- -imides then might be combined to'tetrasubstituted-tricarbodiimide, even though intermediate products form during suchcombination. There are several other methods available for theproduction of these products.

Tctratolyltricarbodiimide seems to be of vsuch stable character that itcan be used For high tensile black.-

32 Smoked sheets.

5 Zinc oxide.

7 Barytes.

E Sulphu'rf Tctratolyltricarbodunncle.

Cure: a l minutes at 40 lbs. steam pressure. Or, 2t) minutes at 40 lbs.steam pressure iorbest aging. v r An unusually high tensile resultsIroin the, list of these cures.

For friction stock.

Smoked sheets. H Sulphur. l /lagnesiuin oxide. 95 Zinc oxide. U fl%%Tetratolyltricarbodnnude.

Cure: 235 minutes at 37 lbs. steam pressure.

For red tube stock,

Smoked sheets.

18 Golden or crimson antimony.

5 Zinc oxide.

'2' Barytes.

(l T tratolyltricarbodiimide. Many of the derivatives of carbod iimidesare cryptocrystalline compounds with the amorphous appearance morefrequently in evidence than the crystalline form, and so they are notreadily. separated from their accon ipanying compounds, that may bepresent due to their origin, or present as byproducts of theirformation.

' Carbodiimide, as well as the phenyl, tolyl, and Xylil substitutionproducts thereof, may some of them assume the form of polymericmodifications.

The use of the term cryptocrystalline in this specification is intendedto designate a body that is at times amorphous, either in fact or inappearance, and yet at other times is of a definite crystalline form.Hidden crystals would be a concise definition.

These cryptocrystallinc carbo-diimide derivatives seem to be generallyof great stability at the temperatures required for vulcanization, havea fairly high nitrogen content, and angoear not to be very reactive withtheir ownby-products during use.

Another characteristic of them is, that :irequeutly they are higher,melting bodies, resulting from the decomposition of lower meltingbodies, which in acceleration. means,

ins-arc? v the original accelerator of lower melting 'point isrogressively decomposed, under vulcanizatlon, into the higher meltingaccelerator, and in theory, eventually the lower melting acceleratorbecomes more or less exhausted and when the cure is completed, thehigher melting accelerating material then present, inhibits the activityof further vulcanization in the cold, or as expressed in technicalparlance the resultant rubber product thus has better agialg qualitiesor stands aging better.

. My invention then consists in utilizing, in

rubber vulcanization, the bodies herein mentioned and which appear tohave superior qualities to many of the compounding ingredients usedheretofore in compounding and vulcanizing rubber.

While I have described my invention in detail, and stated the .znannerin which the products mentioned may be repared. and used,-it is to beunderstood that I do not mean to be limited in this specification to theuse of the particular ingredients mentioned examples, or in any way,except by the claims as set forth and annexed herewith.

It is further to be understood that my invcntion is not to be construedas dependent on the accuracy or soundnessot any of the theories hereinexpressed or on the correct- 95 ness of the structural formulas used todos ignate the products.

Having now described my invention and having shown in what manner thesame may be utilized, what I claim as new, and desire to secure byLetters Patent is:

1. A process of vulcanizin rubber which consists in, incorporating a vuca-nizing agent with rubber, then under heat, accelerating vulcanizationin the presence of tetraxyliltricarbodiimide in the rubber mixture.

2. A process of vulcanizing rubber which consists in, incorporatingtetraxyliltricarbodiiinide, either by itself or in combination withanother organic solid'into rubber as an, 119 aid to vulcanization, thenheating the resultant rubber mixture with a vulcanizing agent to efiectvulcanization.

3. A. process of vulcanizing rubber which consists in, incorporating avulcanizing agent with compounded rubber, then under heat,- causing; theformation of tetraxyliltricarbodiimide within the rubber mixture whileeffecting vulcanization.

tetraxyiiitricarbodiimide throu h combination with another organic soiiso that it may be used as an accelerator, then incorporating theaccelerator thus formeoi into rubber, then heating the resultant rubbermixture with n vulcanizing agent to effect vulcanization.

6. A process of vuicanizing rubber which consists in, incorporating intorubber an accelera'wr resulting from a combination oi desuiphurizcdni0ncand dixylilthiouree, then iiestin the resultant rubber mixture witha. vuicemzing agent to eflect vulcanization.

3, A process of vulcanizing rubber which consists in, incorporating intorubber an accelerator resulting from a dixylilthiouren that has beendesulphurized in the presence of xyiii mustard oil and ammonia, thenheatin the resultant rubber mixture with e vulcamzing agent to eifectvulcanization.

8. A process of vulcanizing rubber which consists in, incorporating intorubber an aci celerator resulting from a combination of 9. A vulcanizedcoi'l'ipcund, nntuini-ng rubber or similar material, a vuicenizing.

agent, and tetraxyiiitricerbodiiinidc.

10. A vulcanized compound, containing rubber or similar material, avuicanizing agent, and a combination of desuipburized monoanddixyiilthiourezi.

1L A vulcanized compound, containing rubber or similar material, evulcanizing agent, and a dixyiiithiourea that has been desulpburized inthe presence of xylil muscard oil and ammonia.

12. A vulcanized compound, containing rubber or similar material avulcanizing agent, and a, combination of carboznonoandcarbcdixyliiiinide, or of their poly meric mociifications respectively.GEORGE H. STEVENS;

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